- Knowing the fundamental of js. This is a must, since this is js. lol
- Learn how to design and implement rest api
- Learn the basic concepts of nodejs (event loop, single thread), it's advantage and disadvantages.
- Know atleast 1 framework, preferably expressjs. (This is not necessarily to learn, as long as you have a solid understanding of how nodejs works)
- Learn any of two db's (mongo or sql) or maybe both.
And last but not the least, before the interview, get your hands dirty (practice practice practice!!!), building some stuff that is built on nodejs, maybe you can showcase it to your interviewer.
Goodluck :D